The java.util.regex package of java provides various classes to find particular patterns in character sequences.
The pattern class of this package is a compiled representation of a regular expression. To match a regular expression with a String this class provides two methods namely −
compile() − This method accepts a string representing a regular expression and returns an object of the Pattern object.
matcher() − This method accepts a String value and creates a matcher object which matches the given String to the pattern represented by the current pattern object.
Following is the regular expression to match date in dd-MM-yyyy format:
^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$Therefore, to validate a date String of the format MM-DD-YYYY −
Compile the above mentioned regular expression using the compile() method of the Pattern class and retrieve the Pattern object.
Using the object obtained above, invoke the matcher() method by passing the required date string as a parameter and retrieve the Matcher object from this method.
The matches() of the Matcher class returns true in case of a match else, it returns false. Invoker this method on the matcher object obtained from the previous step.
Example
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MatchingDate {
public static void main(String[] args) {
String date = "01/12/2019";
String regex = "^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$";
//Creating a pattern object
Pattern pattern = Pattern.compile(regex);
//Matching the compiled pattern in the String
Matcher matcher = pattern.matcher(date);
boolean bool = matcher.matches();
if(bool) {
System.out.println("Date is valid");
} else {
System.out.println("Date is not valid");
}
}
}Output
Date is valid